System and method for controlling solar powered smart windows

ABSTRACT

A solar powered smart window includes a light diffuser configured to convert an incident direct solar radiation to a diffusive light toward interior direction, a light diffuser positioner, a driving mechanism, a solar panel, and a control unit. The control unit moved the light diffuser from a predetermined opened position to a closed position and to hold the light diffuser at the closed position with latch mechanism, when the output power of the solar panel exceeds a threshold for over a duration time. The controller releases the latch mechanism and to cause the light diffuser to return to the predetermined opened position when the output power lowers below threshold for over the duration time. A method includes storing a predetermined condition, monitoring the output power, comparing the output power with the predetermined conditions, making decision whether a positional transition is necessary, and causing the transitional transition or maintaining current position.

BACKGROUND Technical Field

The present disclosure is directed to smart windows with automatedwindow coverings and powered by solar panels.

Description of the Related Art

Growth in population and the enhancement in building services andcomfort levels have increased energy consumption in buildings. Buildingsand construction together account for 36% of global energy use. In atypical office building, artificial lighting consumes the bulk of theenergy followed by cooling and heating operations. See, InternationalEnergy Agency, Global Status Report 2017, and Key World EnergyStatistics 2014. Office buildings have a relatively high proportion oflighting energy consumption per unit area due to their functional andoperational requirements as described in H. Hens, “Thermal comfort inoffice buildings: two case studies commented,” Build. Environ. 44 (2009)1399-1408.

Daylight received through windows can significantly reduce lightingenergy consumption in office buildings. See M. T. Ke, C.-H. Yeh, J.-T.Jian, “Analysis of building energy consumption parameter and energysavings measurement and verification by applying Quest software,” EnergyBuild. 61 (2013) 100-107, the entire contents of which are incorporatedherein by reference. Daylighting provides a pleasant and attractiveindoor environment that can foster higher productivity and performanceas described in P. Plympton, S. Conway, K. Epstein, “Daylighting inSchools: Improving Student Performance and Health at a Price Schools CanAfford,” National Renewable Energy Laboratory Report, CP-550-28059,Golden, Colo., 2000.

Realizing an indoor environment with visual comfort by admittingdaylight through windows requires both a) control of interior brightnessand b) suppression of glare. The former can be realized by adjustinginterior electric lighting depending on the amount of daylight admittedthorough windows. The latter requires blocking direct solar radiationwhich is known to be the primary cause of glare. See U.S. Pat. No.5,663,621 to Popat, the entire contents of which are incorporated hereinby reference. Popat analyzed then known approaches for automatic windowcoverings or “smart windows,” and pointed out their disadvantages: thebrightness regulating systems merely regulate brightness but do notblock direct solar radiation; glare blocking systems requiremodifications of conventional louvers and prevent independent adjustmentof transmitted daylight; integrated systems either do not addresspreventing glare caused by the direct solar radiation, or requirecomplicate systems including sensors and interconnection to lightingsystem. Based on such analysis Popat disclosed a controlling method ofan electronically controlled window covering which can block directsolar radiation while admitting substantial diffuse illumination,utilizing a controller which pre-stored data defining a desired settingof louver angle as a function of the time of the day and the day of theyear, for the prevailing latitude, longitude, and window azimuthorientation, and based on measured results on the exterior brightness.

On the other hand, renewable energy deployment and policies to modernizeelectricity production and consumption are propelling numerous advancesin energy efficient buildings. Renewable energy includes solar and windpower, biomass and so on. Inherent loss due to transmitting power overlong distances makes onsite power generation attractive, especiallysolar power. Solar panels may be placed on the roof of a residentialhome, or commercial building, and connected to the building's or themunicipal power grid, thereby providing electricity for onsiteconsumption.

Several U.S. patents disclose apparatus which integrate solar cells intowindow coverings. For example, U.S. Pat. Pub. No. 2014/0116497A1discloses an onsite solar power generation apparatus configured as aninterior window covering. The electric power generated by the solarcells is converted to AC power and provided to the building power grid.U.S. Pat. No. 7,617,857 discloses venetian blinds with solar cellsmounted on top surfaces of the controller and an adjustment mechanism ofthe slat position and orientation to control the amount of light thevenetian blinds permits to pass inside. The solar cells are configuredto output power to a battery which then is configured to drive LEDsattached to the slats for providing indoor lighting.

Chinese Pat. Pub. CN102865030B disclosed a solar driven shutter withsolar cells mounted on the louver, a drive mechanism for turning andlifting movement of the louvers using the collected solar energy, and acontrol device configured to operate based on a light sensor output anda pre-installed light intensity.

On the other hand, a diffuser (also called a light diffuser or opticaldiffuser) is known in optics field as a material that diffuses orscatters light to transmit soft light. A diffractive diffuser thatexploits the principles of diffraction and refraction with micro surfacestructures has been developed for engineering a specificspatial-configuration and intensity profile of light sources. Thediffractive diffusers are commonly used in commercially available LEDillumination systems. Usually, the diffuser material is GaN or fusedsilica with processed rough surfaces. Even a laser beam is reported tobe converted to a divergent diffused light. See for example,https://en.wikipedia.org/wiki/Diffuser_(optics) andhttp://www.agc.com/en/products/electoric/detail/doe_and_diffuser.html,the entire contents of which are incorporated herein by reference.

Conventional systems such as those described above still do notadequately address the needs and demands of modern energy efficientbuildings which are ideally energy neutral with respect to energyconsumption/generation for lighting and/or heating/cooling. Accordinglyit is one object of the present disclosure to provide a system andmethod for controlling lightning using a smart window that receiveselectrical power from solar cells integrated thereon.

SUMMARY

In an exemplary implementation, a solar powered smart window for awindow of a building includes a light diffuser configured to convert anincident direct solar radiation to a diffusive light toward interiordirection and situated at a predetermined opened position, a lightdiffuser positioner, a driving mechanism including a motor and atransmission mechanism, a solar panel placed at a proximity of thewindow, a control unit configured to receive and monitor an output powerof the solar panel and to compare with a predetermined threshold outputpower of the solar panel. The controller is further configured to movethe light diffuser to a closed position via the light diffuserpositioner and the driving mechanism, and to hold the light diffuser atthe closed position with a latch mechanism, when the output power of thesolar panel is not smaller than the predetermined output power forlonger than a predetermined duration time while the light diffuser is atthe predetermined opened position. The controller is further configuredto release the latch mechanism and to cause the light diffuser to returnto the predetermined opened position when the output power of the solarpanel lowers to a value smaller than the predetermined output power forlonger than the predetermined duration time while the light diffuser isat the closed position.

In another exemplary embodiment, a method includes storing apredetermined condition to cause a positional transition of the lightdiffuser and a positional information of a predetermined opened positionas an initial condition; monitoring the output power of the solar panel;comparing the output power of the solar panel with a predeterminedvalue; making decision whether a positional transition is necessary forthe light diffuser; and either a) causing a transition of the lightdiffuser from the predetermined opened position to a closed position viathe driving mechanism, when the output power of the solar panel is notsmaller than the predetermined value for longer than a predeterminedtime duration while the light diffuser is at the predetermined openedposition; b) causing a return of the light diffuser from the closedposition to the predetermined opened position when the output power ofthe solar panel is smaller than the predetermined value for longer thanthe predetermined time duration, or c) maintaining a current positionwhen either of conditions for above a) or b) is not satisfied.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present disclosure and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1A illustrates schematically a structure of a smart window coveringshown in a front view according to a certain embodiment of the presentdisclosure;

FIG. 1B illustrates schematically a structure of a smart window coveringshown in a side view according to a certain embodiment of the presentdisclosure;

FIG. 2 illustrates schematically an exemplified block diagram of adriving mechanism (A) and a latch mechanism (B) of the smart windowcovering according to the embodiment of the present disclosure;

FIG. 3 illustrates an exemplified block diagram of the control unit 160of the smart window covering of the embodiment of the presentdisclosure;

FIG. 4A illustrates schematically the predetermined opened position (A)of the light diffuser in the embodiment of FIG. 1;

FIG. 4B illustrates schematically the predetermined closed position (B)of the light diffuser in the embodiment of FIG. 1;

FIG. 5A illustrates schematically a structure and operation principle ofthe light diffuser for a certain embodiment of the present disclosure;

FIG. 5B illustrates schematically a structure and operation principle ofthe light diffuser for a certain embodiment of the present disclosure;

FIG. 6A illustrates schematically a structure of the smart windowcovering according to a certain embodiment of the present disclosure as(A) a front view from interior at a closed position;

FIG. 6B illustrates schematically a structure of the smart windowcovering according to a certain embodiment of the present disclosure as(B) a side view at the closed position;

FIG. 6C illustrates schematically a structure of the smart windowcovering according to a certain embodiment of the present disclosure as(C) a side view at the predetermined opened position;

FIG. 7A illustrates schematically a smart window covering according to acertain embodiment the present disclosure as (A) a front view frominterior;

FIG. 7B illustrates schematically a smart window covering according to acertain embodiment the present disclosure as (B) a side view; and

FIG. 8 is an exemplary flow chart of a controlling method for a solarpowered window covering according to a certain embodiment of the presentdisclosure.

DETAILED DESCRIPTION

In the drawings, like reference numerals designate identical orcorresponding parts throughout the several views. Further, as usedherein, the words “a,” “an” and the like generally carry a meaning of“one or more,” unless stated otherwise. The drawings are generally drawnto scale unless specified otherwise or illustrating schematic structuresor flowcharts.

Furthermore, the terms “approximately,” “approximate,” “about,” andsimilar terms generally refer to ranges that include the identifiedvalue within a margin of 20%, 10%, or preferably 5%, and any valuestherebetween.

Aspects of this disclosure are directed to a system of solar poweredsmart window covering for buildings and method for controlling the same.As briefed in the background, conventional approaches of integratingsolar cells into automatic window coverings r utilize solar power todrive an adjusting mechanism of louver angle and position to control theamount of light admitted into the interior. However, they do not providesolutions to maximize the diffused light admitted into the interiorunder condition of blocking direct solar radiation. It is understoodthat conventional opaque metal venetian louvers aligned at an angle toblock direct solar radiation and not to block any diffusive light whenviewed at an interior location close to the window, for example, in factdo fully block the diffusive light when viewed from an interior locationfar from the window.

Accordingly, one embodiment of the present disclosure provides asolution for a solar powered window covering which can maximize thediffusive light admitted into the interior while simultaneously blockingdirect solar radiation, and which therefore can contribute to reducingthe consumption of energy for lighting in buildings. Another embodimentof the present disclosure provides a solution for a solar powered windowcovering which can control the amount of infra-red radiation admittedthrough the window that is accompanied with the solar radiation. Thissolution also contributes to reducing energy for cooling interior air inhot climates, seasons or areas.

FIG. 1 illustrates schematically a structure of a smart window covering100 according to an embodiment of the present disclosure. Here (A)illustrates a front view from interior side and (B), a left side view atsection X-X′. The smart window covering 100 according to the embodimentincludes a solar panel 120, a light diffuser 130, a light diffuserpositioner 140, a driving mechanism 150, and a control unit 160.

The smart window covering 100 may include a frame 110 configured to beattached to a window frame and including an upper horizontal frame 111,a bottom horizontal frame 112, and a pair of side frames 113. The frame110 may be substituted by a window frame of a building. The solar panel120 is attached to a proximity of the frame of the window, here in theembodiment, mounted on the bottom horizontal frame 112.

The light diffuser 130 includes a base plate 131 transparent for visiblelight; and a light diffusing element 132 which is configured to convertan incident direct solar radiation to a diffusive light toward interior.The light diffuser is configured to stay at a predetermined openedposition initially and to move to a closed position when predeterminedconditions are satisfied. The light diffuser is configured to blockdirect solar radiation and converts to the diffusive light at the closedposition, as detailed in FIG. 2. The light diffuser 130 is furtherconfigured to return to the predetermined opened position when certainconditions are satisfied: namely when there is no need of blocking thedirect solar radiation.

The light diffuser positioner 140 is configured to move the lightdiffuser 130 between the predetermined opened position and the closedposition, where the light diffuser positioner 140 is configured to bedriven by the driving mechanism 150 under a control of the control unit160. The light diffuser positioner 140 includes a supporting member 141comprising a rigid material, a pair of pin shafts 142 embedded into thepair of side frame 113, a pair of vertical rods 143 with a plurality ofside ports 144, an upper horizontal solid rod 145 connecting the pair ofvertical solid rods at upper ends thereof, and a center verticalconnection member 146 made of a solid rod or a string connecting theupper horizontal solid rod 145 at a center portion of the upperhorizontal sold rod 145 with the driving mechanism 150. An end of thesupporting member 141 is perpendicularly fixed to a base plate 131 ofthe light diffuser 130, where the supporting member 141 is rotatablyattached to one of a pair of side frames 113 with a pin shaft 142perpendicularly embedded into the one of the pair of side frames 113 ata portion between both ends of the supporting member 141. The other endof the supporting member 141 is connected rotatably and slidably to oneof the plurality of side ports 144 of the vertical solid rod 143.

Each of the pair of vertical solid rods 143 may be vertically slidablyconnected to each of the pair of side frames 113 at around a bottom endportion of the each of pair of the vertical solid rods 143 with one of apair of pin shafts 147 perpendicularly embedded into each of the pair ofside frames 113.

The driving mechanism 150 of the light diffuser positioner includes amotor 151, a latch mechanism 152 to latch a motion of the drivingmechanism, and a transmission mechanism 153 to transmit the motion ofthe motor 151 to the light diffuser positioner 140.

The control unit 160 is configured to move the light diffuser 130 to theclosed position via the light diffuser positioner 140 and to hold thelight diffuser 130 at the closed position using the latch mechanism 152,when the output power of the solar panel 120 is not smaller than thepredetermined output power for longer than the predetermined durationtime while the light diffuser is at the predetermined opened position.On the other hand, the control unit 160 is also configured to releasethe latch mechanism and to cause the light diffuser 130 to return to thepredetermined opened position when the output power of the solar panel120 lowers to a value smaller than the predetermined output power forlonger than the predetermined duration time while the light diffuser 130is at the closed position.

FIG. 2 illustrates schematically an exemplified block diagram of adriving mechanism (A) and a latch mechanism (B) of the smart windowcovering according to an embodiment of the present disclosure. Thedriving mechanism 150 includes a motor 151 and a transmission mechanism152. The motor 151 may be a conventional axial rotation motor or alinear motor. The transmission mechanism 152 includes either one of agear transmission or a belt transmission, and a latch mechanism 153configured to hold a motion of the driving mechanism being electricallycontrolled, as illustrated in FIG. 2 (B).

FIG. 3 illustrates an exemplified block diagram of the control unit 160of the smart window covering of the embodiment of the presentdisclosure. The control unit 160 includes a memory 161, a monitor 162 ofthe output power from the solar panel 120, a controller 163, a powersource 164, and a human interface. The memory 161 is configured to storea predetermined threshold output power of the solar panel, apredetermined duration time, and a present position of the lightdiffuser. The monitor 162 is configured to receive an output power fromthe solar panel 120 and send a monitor signal to the controller 163. Thecontroller 163 is configured to control the driving mechanism. The powersource 164 is configured to supply an electric power required for anoperation of the smart window covering. The human interface 165 isconfigured to accept an input for the conditions to be predetermined.The controller may be further configured to manage receiving the outputpower from the solar panel 120 and charging the output power to thepower source 164. The power source may be constituted by a capacitor forenergy storage, a rechargeable battery, or a combination of them, andmay further include a constant-voltage direct-current (DC) power supplycircuit. The power source 164 may also be supplemented by a DC powergenerated by AC to DC regulator 166 of AC power from a commercial grid,and may further be accompanied by a DC/AC inverter to supply a residualpower for domestic or local equipment.

The human interface enables modifications of the preinstalled conditionsincluding the preinstalled threshold output power of the solar panel byusers, based on observations of timings of transitions between thepredetermined opened state and the closed states and the output power ofthe solar panel, under circumstances including seasonal changes of solarlight. Such modifications make the system more user friendly and morematched with actual circumstance of use.

FIG. 4 illustrates schematically the predetermined opened position (A)and the closed position (B) of the light diffuser 130 in the embodimentof FIG. 1. The light diffuser positioner 140 is configured to stay at abottom position of the light diffuser positioner 140 and situate thelight diffuser 130 at the predetermined opened position (A), at initialcondition or when the output power of the solar panel is less than thepredetermined threshold for longer than a predetermined duration timeand hence there is no need of blocking the direct solar right. At thepredetermined opened position (A), the light diffuser 130 is configuredto pass the diffusive light from an opening of the window towardinterior as much as possible. An angle between the surface of the baseplate 131 of the light diffuser 130 and a horizontal surface at thepredetermined opened position may be configured adjustable, for example,by adjusting a length of the center vertical connection member 146.

The control unit 160 is configured to cause an upward motion of thevertical solid rod 143, rotate the light diffuser 130 to the closedposition (B) of FIG. 4 by pulling the center vertical connection member146 via the driving mechanism 150, and to hold the light diffuser 130 atthe closed position (B) using the latch mechanism 153, when followingtwo conditions are satisfied:

-   -   1) the output power of the solar panel is not smaller than the        predetermined output power for longer than the predetermined        duration time; and    -   2) the light diffuser is at the predetermined opened position.        The light diffuser 130 at the closed position (B) is configured        to convert a direct solar radiation incident to the light        diffuser 130 to a diffusive light toward interior direction as        detailed in FIG. 5.

On the other hand, the control unit 160 releases the latch mechanism 153and to cause the light diffuser 130 to return to the predeterminedopened position when following two conditions are satisfied:

-   -   1) the output power of the solar panel lowers to a value smaller        than the predetermined output power for longer than the        predetermined duration time; and    -   2) the light diffuser is at the closed position.        Here the light diffuser 130 is configured to return to the        predetermined opened position by utilizing a weight of the light        diffuser positioner 140. The light diffuser 130 may be        configured to utilize a driving force of the motor via the        driving mechanism 150 when the power source has charged an        enough energy.

FIG. 5 illustrates schematically structures and operation principle ofthe light diffuser 500 for a certain embodiment of the presentdisclosure. The light diffuser (A) includes a base plate 531 transparentfor visible light and a light diffusing element 532 on interior side ofthe base plate. A micro surface structure 532 comprising micro concavelens structures for example, formed on a surface of the base plate 531is configured to convert an incident direct solar radiation to diffusivelights toward interior direction by diffraction and refraction asillustrated by arrows. Such micro structures are generally known asdiffractive diffusers and have applied so far for shaping a beam profileof light sources as briefed in background. The light diffuser (B)further includes a diffractive diffuser 533 made of a transparentplastic sheet and pasted on an interior side surface of the base platein addition to the monolithic micro surface structure 532 formed on thesurface facing exterior side of the base plate 531. As illustrated byarrows, the structure (B) is expected to bring a divergent refractioneffect larger than that of (A). Alternatively, a transparent layer ofinorganic material or compound material including SiO₂ or GaN formed ona surface of the base plate and with a rough surface equivalent to theconcave structure may also be incorporated as the light diffusingelement.

The light diffuser 500 of the smart window coverings of the presentdisclosure may further be configured to reflect and/or absorb aninfra-red (IR) radiation by at least one of an IR reflection coating ona surface of the base plate, doping of IR absorbing metal to the baseplate, or doping of IR absorbing metal oxide to the base plate. See forexample, M. A. Butt, S. A. Fomchenkov, N. L. Kazanskiy, A. Ullah, R. Z.Ali, and M. Habib “Infrared reflective coatings for building andautomobile glass windows for heat protection”, Proc. SPIE 10342, OpticalTechnologies for Telecommunications 2016, 103420O (6 Apr. 2017), theentire contents of which are incorporated herein by reference. In a hotclimate area or during a hot summer season, the IR reflection would beeffective for protection from heat and for reducing energy consumptionfor air-conditioning. However, when an IR absorption approach isincorporated, the solar powered window covering may desirably beinstalled into an exterior side of the window, for realizing aneffective heat protection simultaneously with maximizing theintroduction of diffusive light into interior. Because, heat reflectedor absorbed by the light diffuser would eventually warm up interior airwhen installed interior side. On the other hand, in a cold winter day,introducing heat of the sun light into interior would be helpful to warmup room temperature and to reduce an energy for heating. From suchperspective, it would be also an option to prepare two types of windowcoverings designed for hot climate or for summer season use with IRreflective coating and for cold climate or winter season use without IRreflective coating, and to choose one from the two types depending oneach climate or season.

Regular window glass is known to absorb ultra violet (UV) radiation.When a thickness of the glass is larger than 6 mm, most of UV componentsin the solar radiations are absorbed. In a season when the interior airconditioning is not required, fresh air from an opened window isdesirable. For such a purpose, the smart window covering of the presentdisclosure may optionally have UV blocking in combination with a thickglass plate with thickness over 6 mm as the base plate of the lightdiffuser. Such a window covering would satisfy both requirement ofintroducing the fresh outside air and blocking the direct solarradiation including reflection or absorption of IR and UV components.

FIG. 6 illustrates schematically a structure of the smart windowcovering 600 according to an embodiment of the present disclosure, (A)is a front view from interior at a closed position, (B) is a side viewat the closed position and (C) is a side view at the predeterminedopened position both to left side from section line X-X. A solar panel620 is mounted on the bottom horizontal frame 612 and at a proximity ofa window glass 601. A light diffuser 630 includes a plurality of thebase plates 631 each thereof integrated with the light diffuser element632 as detailed in FIG. 5, the plurality of the base plates 631 attachedto a positioner string 643 of a light diffuser positioner 640.

The light diffuser positioner 640 includes a horizontal rod 641 attachedto the upper horizontal frame 611 rotatably around a center axis of thehorizontal rod 641; a reel 642 fixed to the horizontal rod 641; and thepositioner string 643 made of a flexible material, wherein the drivingmechanism 650 is configured to rotate the horizontal rod 641 and thereel 642 being controlled by the control unit 660. A first end of thepositioner string 643 is configured to be fixed to the reel 642 and thesecond end of the positioner string 643 is configured to be fixed to aproximity of the bottom horizontal frame 612 at a point 660 verticallybelow the reel 642 to which the first end of the positioner string 643is attached. The positioner string 643 is made of the flexible materialfor example, a nylon, and configured to endure repeated usages under atension larger than a weight of the light diffuser. See, for examplehttp://www.chemistryexplained.com/Ny-Pi/Nylon.html, the entire contentsof which are incorporated herein by reference.

Referring FIG. 6 (C), the light diffuser 630 is configured to stay onthe bottom horizontal frame 612 at the predetermined opened position orat an initial condition in a state folded at a gap area 662 betweenadjacent two of the plurality of the base plates 631. The light diffuser630 in the state folded may be configured to be installed in a casing670 mounted on the bottom horizontal frame 612. The base plate 631 ofthe light diffuser 630 is in a rectangular shape with a horizontallength almost equal to but shorter than a horizontal distance betweensurfaces of the pair of the side frames 613, and with a vertical heightsmaller than a reminder of a subtraction of a thickness of the solarpanel 620 from a horizontal depth D of the bottom horizontal frame 612.

Referring now to (A) and (B), the light diffuser 630 is configured todevelop from a predetermined opened position (C) to the closed positionillustrated by (A) and (B), by spooling of the positioner string 643,the spooling made by the rotation of the reel 642 driven by the drivingmechanism 650. At the closed position (A) and (B), the light diffuser630 is configured to cover most of an opening of the frame, where theplurality of the base plates 631 are aligned in a vertical directionwith each thereof being aligned in a horizontal direction.

The light diffuser 630 is configured to return to the predeterminedopened position (C) in a state folded at a gap area 662 between adjacenttwo of the plurality of the base plates, utilizing a weight of the lightdiffuser when the control unit 610 releases the latch mechanism of thedriving mechanism 650. Additionally, the control unit 660 may drive thedriving mechanism to rotate the reel 642 in a direction to help thelight diffuser 630 return to the predetermined opened position (C).

The smart window covering of FIG. 6 may further include a guide string644 connecting straightly and vertically the upper horizontal frame 611and the bottom horizontal frame 612, wherein the guide string 644 isconfigured to pass through a plurality of support rings 645 each thereofattached to a side of a base plate, the side of the base plate facing asame side as the guide string when folded at the predetermined openedposition.

The light diffuser 630 of the smart window covering of FIG. 6 mayfurther include a spring 646, where the spring 646 is attached toadjacent two of the plurality of the base plates 631 and configured tohelp the plurality of the base plates 631 return to the predeterminedposition, namely the folded state.

The light diffuser 630 of the smart window covering of FIG. 6 mayfurther include a diffractive diffuser sheet 633 made of plasticmaterial and covering the gap area between the adjacent two of theplurality of the base plates, where the diffractive diffuser sheet isconfigured to convert the direct solar radiation incident to diffusivelights toward interior.

FIG. 7 illustrates schematically a smart window covering 700 accordingto an embodiment the present disclosure, (A) a front view from interiorand (B) a side view from a section line X-X. A solar panel 720 ismounted on a bottom horizontal frame 712. Each of a pair of side frames713 includes a longitudinal track 780, where the longitudinal tracks 780of the pair of the side frames 713 face one another and each extendscontinuously from a bottom end 781 of the longitudinal track configuredto contact the lower horizontal frame 712 to an upper end 782 of thelongitudinal track located at a proximity of the upper horizontal frame711. Here a frame for the smart window covering 710 is inserted into theframe of the window. However, the frame of the window may substitute forthe upper horizontal frame and the bottom horizontal frame of the smartwindow, except for a pair of side frames 713 which includes thelongitudinal tracks.

The light diffuser 730 includes a single base plate 731 with the lightdiffusing element not illustrated here but formed as described in FIG.3. The single basic plate 731 of the light diffuser 730 has two verticalsides 783, where each of the two vertical sides 783 of the single basicplate is slidably inserted into each of the longitudinal tracks 780 ofthe pair of the side frames 713.

The light diffuser positioner 740 includes a horizontal rod 741 attachedto the upper horizontal frame 711 rotatably around a center axis of thehorizontal rod 741, a pair of reels 742 each fixed to the horizontal rod741 at proximity of each of the pair of side frames 713; and a pair ofpositioner strings 743 made of a flexible material for example, a nylon,and configured to endure repeated usages under a tension larger than aweight of the light diffuser, as described in FIG. 6. A drivingmechanism 750 is configured to rotate the horizontal rod 751 and thereel 752 being controlled by the control unit 760.

An end of the positioner string 743 is fixed to an upper end of thebasic plate of the light diffuser at a location 733 close to one of thetwo vertical side of the basic plates, the other end of the positionerstring is attached to one of the pair of reels 742 configured to besituated vertically above the location 733 where the end of thepositioner string is fixed to the upper end of the basic plate.

The light diffuser 730 is configured to stay on the lower horizontalframe 712 at a predetermined opened position, and move to the upper end782 of the longitudinal tracks at the closed position, where the lightdiffuser 730 is aligned to block the direct solar radiation incident tothe light diffuser and to convert to the diffusive light whenpredetermined conditions are satisfied, and to return to thepredetermined opened position when there is no need of blocking thedirect solar radiation, with the same algorithm as detailed in FIG. 2.

The window covering illustrated in FIG. 7 is a simplified version of thepresent disclosure and may fit for uses in areas with a relatively coolclimate or the replacing use as a winter season version where theheating effect of the sun light is preferably introduced into interiorthrough the window. At the closed position, the light diffuser 730 ofFIG. 7 allows the direct solar radiation entering into interior from alower half portion of the window, which would be acceptable or evenpreferable for example in winter season in warming up interior air,while simultaneously blocking and converting the direct solar radiationincident at a higher portion of the window, which would prevent a glareand help keeping the window bright by introducing only the diffusivelight.

FIG. 8 is an exemplary flow chart of a controlling method for a solarpowered window covering according to a certain embodiment of the presentdisclosure. The method for controlling a smart window with a lightdiffuser configured to be driven by a driving mechanism powered by anoutput power of a solar panel includes providing a predeterminedcondition to cause a positional transition of the light diffuser and apositional information of a predetermined opened position as an initialcondition, monitoring the output power of the solar panel, comparing theoutput power of the solar panel with a predetermined value, making adecision whether a positional transition is necessary for the lightdiffuser; and either a) causing the positional transition of the lightdiffuser from a predetermined opened position to a closed position viathe driving mechanism and updating a position information after thetransition, when the output power of the solar panel is not smaller thanthe predetermined value for longer than a predetermined time durationwhile the light diffuser is at the predetermined opened position, b)causing a return of the light diffuser from the closed position to thepredetermined opened position, and updating a position information afterthe transition, when the output power of the solar panel is smaller thanthe predetermined value for longer than the predetermined time duration,or c) maintaining a current position when neither of condition for a)nor condition for b) is satisfied.

A solar powered window covering which includes the features in theforegoing description provides numerous advantages. The light diffusersdescribed in the present disclosure can block the direct solar radiationand convert it to diffusive light toward interior at the closedposition. Thus, the light diffuser of the present disclosure provides asolution that provides brighter diffusive light in comparison toconventional s that block direct solar radiation. This reduces theconsumption of electric energy for interior lighting. In addition, thepresent disclosure has the advantage of optionally revising an IRreflective layer for summer time or hot climate use. The optional IRreflective layer reduces heat flow from the window due to diffusivelight during summer time, resulting in a reduction of energy forcooling. Further, the control method of the present disclosure does notrequire other complicated sensors for monitoring the output power of thesolar panel. This feature enables adjusting of the preinstalledthreshold output power of the solar panel based on an installedcircumstance and seasonal changes of output power of the solar lightreferring the monitored output power of the solar panel. The controllingalgorithm of the present disclosure realizes a more flexible and thususer-friendly system.

Obviously, numerous modifications and variations are possible in lightof the above teachings. It is therefore to be understood that within thescope of the appended claims, the invention may be practiced otherwisethan as specifically described herein. Thus, the foregoing discussiondiscloses and describes merely exemplary embodiments of the presentinvention. As will be understood by those skilled in the art, thepresent invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof.Accordingly, the disclosure of the present invention is intended to beillustrative, but not limiting of the scope of the invention, as well asother claims. The disclosure, including any readily discernible variantsof the teachings herein, define, in part, the scope of the foregoingclaim terminology such that no inventive subject matter is dedicated tothe public.

1. A smart window covering for an exterior window of a building, thesmart window covering comprising: a light diffuser comprising: a baseplate transparent to visible light, and a light diffusing elementconfigured to convert incident direct solar radiation to a diffusivelight toward an interior direction of the building, wherein the lightdiffuser is aligned at a predetermined opened position initially; alight diffuser positioner configured to move the light diffuser betweenthe predetermined opened position and a closed position; a drivingmechanism of the light diffuser positioner, the driving mechanismcomprising a motor, a latch mechanism configured to latch a motion ofthe driving mechanism, and a transmission mechanism configured totransmit the motion of the motor to the light diffuser positioner; asolar panel configured to be attached at a proximity of the window toreceive a solar light; and a control unit further comprising a memory, amonitor of an output power from the solar panel, a controller and apower source, wherein the memory is configured to store a predeterminedthreshold output power of the solar panel, a predetermined durationtime, and a present position of the light diffuser, wherein the monitoris configured to receive an output power from the solar panel and send amonitor signal to the controller, wherein the controller is configuredto control the driving mechanism, and wherein the power source isconfigured to supply an electric power required for an operation of thesmart window covering, wherein the control unit is further configured tomove the light diffuser to the closed position via the light diffuserpositioner and the driving mechanism, and to hold the light diffuser atthe closed position with the latch mechanism when following twoconditions are satisfied: 1) the output power of the solar panel is notsmaller than the predetermined output power for longer than thepredetermined duration time; and 2) the light diffuser is at thepredetermined opened position, and wherein the control unit is furtherconfigured to release the latch mechanism and to cause the lightdiffuser to return to the predetermined opened position when followingtwo conditions are satisfied: 1) the output power of the solar panellowers to a value smaller than the predetermined output power for longerthan the predetermined duration time; and 2) the light diffuser is atthe closed position.
 2. The smart window covering of claim 1, whereinthe power source comprises at least one of a capacitor for energystorage and a rechargeable battery.
 3. The smart window covering of theclaim 1, wherein the light diffusing element further comprises at leastone of a monolithic diffractive diffuser formed monolithically on asurface of the base plate, a diffractive diffuser made of plastic sheetand pasted on a surface of the base plate, and a transparent inorganicmaterial layer with a concave surface formed on a surface of the baseplate.
 4. The smart window covering of the claim 1, wherein the lightdiffuser positioner further comprises a supporting member made of asolid material; a pair of vertical solid rods with a plurality of sideports; an upper horizontal solid rod connecting the pair of verticalsolid rods at upper ends thereof; and a center vertical connectionmember made of a solid rod or a string connecting the upper horizontalsolid rod at a center portion thereof with the transmission mechanismconfigured to be attached to an upper horizontal frame of the window,wherein the supporting member is attached to the base plate of the lightdiffuser at one end of the supporting member, and also connectedrotatably and slidably to one of the plurality of the side ports of thevertical solid rod at the other end of the supporting member, andfurther rotatably attached to one of a pair of side frame of the windowwith a pin shaft perpendicularly embedded into and fixed to the one ofthe pair of side frame of the window at a portion between both ends ofthe supporting member, wherein the light diffuser positioner isconfigured to stay at a bottom position of the light diffuser positionercorresponding to the predetermined opened position of the lightdiffuser, wherein the control unit is configured to make rotate thelight diffuser to the closed position by lifting the pair of verticalsolid rods with the plurality of side ports up to an upper position ofthe light diffuser positioner by pulling by the center verticalconnection member via the transmission mechanism, and wherein the lightdiffuser positioner is further configured to return to the bottomposition of the light diffuser positioner utilizing a weight of thelight diffuser positioner when the control unit releases the latchmechanism.
 5. The smart window covering of the claim 4, wherein each ofthe pair of vertical solid rods is vertically slidably connected to eachof the pair of side frames at around a bottom end portion of the each ofpair of the vertical solid rods with a pin shaft perpendicularlyembedded into each of the pair of side frames.
 6. The smart windowcovering of the claim 4, wherein an angle between the surface of thebase plate of the light diffuser and a horizontal surface at thepredetermined opened position is configured adjustable.
 7. The smartwindow covering of the claim 1, wherein the light diffuser positionerfurther comprises a horizontal rod attached to an upper horizontal frameof the window rotatably around a center axis of the horizontal rod; areel fixed to the horizontal rod; and a positioner string made of aflexible material, wherein the driving mechanism is configured to beattached to the upper horizontal frame of the window, and to rotate thehorizontal rod and the reel being controlled by the control unit,wherein a first end of the positioner string is configured to be fixedto the reel and the second end of the positioner string is configured tobe fixed to a proximity of a bottom horizontal frame of the window,vertically below the reel to which the first end of the positionerstring is attached, wherein the base plate of the light diffuser is in arectangular shape with a horizontal length almost equal to but shorterthan a horizontal distance between surfaces of a pair of side frames ofthe window, and with a vertical height smaller than a reminder of asubtraction of a thickness of the solar panel from a horizontal depth ofthe bottom horizontal frame, wherein the light diffuser comprising aplurality of the base plates each being integrated with the lightdiffuser element, the plurality of the base plates attached to thepositioner string, wherein the light diffuser is configured to stay onthe bottom horizontal frame at the predetermined opened position in afolded state at a gap area between adjacent two of the plurality of thebase plates, wherein the control unit is configured to develop theplurality of the base plates to the closed position of the lightdiffuser from the predetermined opened position by spooling thepositioner string by rotating of the reel via the driving mechanism,wherein wherein the light diffuser is further configured to cover mostof an opening of the window at the closed position, the plurality of thebase plates being aligned in a vertical direction with each beingaligned in a horizontal direction, and return to the predeterminedopened position in the folded state, utilizing a weight of the lightdiffuser when the controller released the latch mechanism.
 8. The smartwindow covering of the claim 7, wherein the light diffuser is configuredto be installed in a bottom casing mounted on the bottom horizontalframe.
 9. The smart window covering of the claim 7, further comprising aguide string connecting straightly and vertically the bottom horizontalframe and the upper horizontal frame, wherein the guide string isconfigured to pass through a plurality of rings each thereof attached toa side of a base plate, the side of the base plate facing a same side asthe guide string in the state folded at the predetermined openedposition.
 10. The smart window covering of the claim 7, furthercomprising a spring, wherein the spring is attached to adjacent two ofthe plurality of the base plates and configured to return the pluralityof the base plates to the folded state.
 11. The smart window covering ofthe claim 7, wherein the light diffusing element further comprising adiffractive diffuser sheet made of plastic material and covering the gaparea between the adjacent two of the plurality of the base plates. 12.The smart window covering of the claim 1, further comprising a pair ofside frames configured to be inserted into both sides of the windowvertically, wherein each of the pair of side frames comprises alongitudinal track, wherein the longitudinal tracks of the pair of theside frames face one another and extend continuously from a bottom endof the longitudinal tracks to an upper end of the longitudinal tracks,wherein the bottom end is located at a lower horizontal frame of thewindow, and an upper end of the longitudinal tracks located proximity ofan upper horizontal frame of the window, wherein the light diffusercomprises a basic plate with two vertical sides of the basic plates,wherein each of the two vertical sides of the basic plates is slidablyinserted into each of the longitudinal tracks of the pair of the sideframes, wherein the light diffuser positioner further comprises ahorizontal rod attached to the upper horizontal frame rotatably around acenter axis of the horizontal rod; a pair of reels each fixed to thehorizontal rod at proximity of each of the pair of side frames; and apair of positioner strings made of a flexible material, wherein thedriving mechanism is configured be attached to the upper horizontalframe and to rotate the horizontal rod and the reel being controlled bythe control unit, wherein a first end of the positioner string is fixedto an upper end of the basic plate of the light diffuser at a locationclose to one of the two vertical sides of the basic plates, the otherend of the positioner string is fixed to one of the pair of reelsconfigured to be situated vertically above the location where the oneend of the positioner string is fixed to the upper end of the basicplate, wherein the light diffuser is configured to stay at a lowestposition in the longitudinal tracks at the predetermined openedposition, the control unit is configured to move the light diffuser tothe upper end of the longitudinal tracks at the closed position of thelight diffuser, and the light diffuser is further configured to returnto the lowest position in the longitudinal tracks utilizing a weight ofthe light diffuser when the control unit releases the latch mechanism.13. The smart window coverings of the claim 3, wherein the lightdiffuser is further configured to reflect and/or absorb an infra-red(IR) radiation by at least one of an IR reflection coating on a surfaceof the base plate, doping of IR absorbing metal to the base plate, ordoping of IR absorbing metal oxide to the base plate.
 14. The smartwindow coverings of the claim 1, wherein the motor comprises aconventional axial rotation type motor or a linear motor.
 15. The smartwindow coverings of the claim 2, wherein the power source is configuredto be supplemented by DC power from a commercial grid.
 16. The smartwindow covering of the claim 1, wherein the light diffuser positionerfurther comprises a supporting member made of a solid material; a pairof horizontal solid rods with a plurality of side ports; a verticalsolid rod connecting the pair of horizontal solid rods at right sideends thereof; and a center horizontal connection member made of a solidrod connecting the vertical solid rod at a center portion thereof withthe transmission mechanism attached to a right side frame of the window,wherein the supporting member is rigidly fixed to the base plate of thelight diffuser at one end of the supporting member, and also connectedrotatably and slidably to one of the plurality of the side ports of thehorizontal solid rod at the other end of the supporting member, andfurther rotatably attached to one of a pair of horizontal frames of thewindow with a pin shaft perpendicularly embedded into and fixed to theone of pair of the horizontal frames at a portion between both ends ofthe supporting member, wherein the light diffuser positioner isconfigured to stay at an opened position of the light diffuserpositioner when the light diffuser stays at the predetermined openedposition, wherein the control unit is configured to make rotate thelight diffuser to the closed position by pulling rightward the pair ofhorizontal slid rods with the plurality of side ports by the centerhorizontal connection member via the transmission mechanism, whereinfurther, wherein the light diffuser is configured to return to thepredetermined opened position of the light diffuser positioner beingpushed by the center horizontal connection member via the transmissionmechanism when the controller releases the latch mechanism.
 17. Thesmart window covering of the claim 16, wherein each of the pair ofhorizontal solid rods is horizontally slidably connected to each of thepair of horizontal frames at around a left side end portion of the eachof pair of the horizontal solid rods with a pin shaft perpendicularlyembedded into each of the pair of horizontal frames.
 18. The smartwindow covering of claim 1 further comprising a rectangular frame of thesmart window covering configured to be inserted into the window.
 19. Amethod for controlling a smart window with a light diffuser configuredto be driven by a driving mechanism powered by an output power of asolar panel, the method comprising: storing a predetermined condition tocause a positional transition of the light diffuser and a positionalinformation of a predetermined opened position as an initial condition;monitoring the output power of the solar panel; comparing the outputpower of the solar panel with a predetermined value; making decisionwhether a positional transition is necessary for the light diffuser; andeither a) causing a transition of the light diffuser from thepredetermined opened position to a closed position via the drivingmechanism, when the output power of the solar panel is not smaller thanthe predetermined value for longer than a predetermined time durationwhile the light diffuser is at the predetermined opened position; b)causing a return of the light diffuser from the closed position to thepredetermined opened position when the output power of the solar panelis smaller than the predetermined value for longer than thepredetermined time duration, or c) maintaining a current position whenconditions for a) or b) is not satisfied.
 20. The smart window coveringof the claim 3, wherein the light diffuser is further configured toreflect and/or absorb an ultra-violet (UV) radiation by at least one ofadopting a glass sheet with a thickness over 6 mm as the basic plate ofthe light diffuser, coating a UV reflection layer to the basic plate.